x86-64, unistd: Remove bogus __IGNORE_getcpu

The change:

commit fce8dc06423d6fb2709469dc5c55b04e09c1d126
Author: Andy Lutomirski <luto@mit.edu>
Date:   Wed Aug 10 11:15:31 2011 -0400

    x86-64: Wire up getcpu syscall

added getcpu as a real syscall, so we shouldn't ignore it any more.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/b4cb60ef45db3a675a0e2b9d51bcb022b0a9ab9c.1314195481.git.luto@mit.edu
Reported-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>